Study of addition aluminium dummy in central irradiation position (CIP) on RSG-GAS reactor neutronic operation parameters

The RSG-GAS reactor is a research reactor operated for radioisotope production, neutron activation analysis, research and material testing. The RSG-GAS reactor operates for 625 MWd each cycle and core fuel management uses a 5/1 pattern in the fuel loading. Every fuels replacement in the reactor core performed calculating and measured reactor parameters to determine the safety factor of reactor operation. Under normal operating conditions the irradiation facility is in a water or aluminium dummy. The addition of aluminum dummy to the irradiation facility needs to be known for its effect on the neutronic parameters of the RSG-GAS reactor. In this paper, we evaluated the calculation and measurement of reactor operating parameters and the dummy effect of aluminium on reactivity and neutron flux of 97 RSG-GAS reactors core. The calculation of operating parameters is done using a combination of WIMS/D5 for the cell generation cross section, Batan-2DIFF to calculate reactivity, radial power peacking factor and Batan-3DIFF to calculate the axial power peacking factor and neutron flux in the reactor core. Based on the results of calculations and measurements indicate that the 97 RSG-GAS reactors core meets the reactor operating safety limit. The reactivity effect due to the placement of the aluminium dummy on the CIP 0.17 % Δk/k. If the aluminium dummy is placed in the CIP and the IP will increase the flux in that position because aluminium has a very good moderating power. The value of power factor for peak radial and axial power is 1.2200 and 1.2902, respectively. The value is still within the safety limit of reactor operations. (author)